A scanning tunneling microscope with stable imaging and scanning imaging method

Abstract

The present invention belongs to the technical field of scanning tunneling microscopes, and in particular relates to a scanning tunneling microscope with stable imaging and a scanning imaging method. A scanning tunneling microscope with stable imaging includes a mirror body, which includes an outer frame, a driving unit, a sliding unit, a sample holder, and a scanning unit. The outer frame is hollow inside, and the driving unit and the sample holder are respectively arranged at the two ends inside the outer frame. The sliding unit is arranged on the inner side wall of the outer frame. The scanning unit is fixedly arranged at one end of the sliding unit close to the sample holder. The driving unit drives the sliding unit to push the scanning unit to advance or withdraw the needle along the length direction of the outer frame. The present invention can improve the quality and stability of imaging and avoid the occurrence of needle collision as much as possible.

Description

Technical Field

[0001] The present invention belongs to the technical field of scanning tunneling microscopes, and in particular relates to a scanning tunneling microscope with stable imaging and a scanning imaging method. Background Art

[0002] A scanning tunneling microscope (STM) uses a sharp conductive probe to scan the surface of a sample. A tunnel junction is formed between the sample and the needle tip, and the distance between the sample and the needle tip is less than one nanometer. At this time, the electron cloud on the sample surface overlaps with the electron cloud at the tip of the needle tip. At this time, a bias voltage is applied between the sample and the needle tip, which generates a tunnel current. This tunnel current is then used to detect the electron state density and atomic arrangement on the sample surface for microscopic imaging.

[0003] Strong magnetic fields can influence the orientation and motion of electron and nuclear spins within matter, facilitating the study of its structure, properties, and interactions. High-magnetic field research can probe properties such as magnetism, superconductivity, and spin states, furthering the development of materials science and condensed matter physics. Therefore, the use of scanning tunneling microscopy (STM) to observe and study magnetic materials, magnetic nanostructures, quantum spin states, and superconductor properties under high magnetic fields facilitates in-depth exploration of the microscopic mechanisms of magnetic materials and quantum phenomena, driving the development of magnetic materials science and nanotechnology. Water-cooled magnetic fields capable of generating magnetic field strengths exceeding 30 Tesla have gradually become the preferred high-magnetic field for research.

[0004] However, existing STMs are subject to significant mechanical vibration during operation. For example, in existing STMs, an inertial motor directly drives the serial scanning units to advance the needle. This drive method inherently relies on rapid changes in acceleration, which causes the inertial motor to produce large step lengths during the stepping process, resulting in severe mechanical vibration in the scanning unit. Furthermore, mechanical vibration can be caused by resonance of the STM gantry and noise from electromechanical components. Turbulent cooling water in a water-cooled magnetic field can also introduce strong environmental vibrations. Furthermore, the piezoelectric element in existing STMs can also experience thermal drift and thermal fluctuations during operation, which are transmitted to the serial scanning units. These interference factors, including mechanical vibration, environmental vibration, thermal drift, and thermal fluctuations, can cause the STM probe to accidentally contact the sample surface during needle advancement, a phenomenon known as needle strikes. These strikes can not only damage the probe tip and alter the sample's topography, but can also cause subtle shifts in the probe or sample position, blurring or distorting high-resolution atomic-level imaging and compromising accurate observation of sample surface features. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a scanning tunneling microscope with stable imaging, which can reduce the interference in the scanning tunneling microscope body, improve the quality and stability of imaging, and avoid the occurrence of pin collision as much as possible.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A scanning tunneling microscope with stable imaging includes a mirror body, a signal acquisition and drive module, and a computer. The mirror body and the signal acquisition and drive module are electrically connected. The mirror body includes an outer frame, a drive unit, a sliding unit, a sample holder, and a scanning unit. The outer frame is hollow inside. The drive unit and the sample holder are respectively arranged at two ends inside the outer frame. The sliding unit is arranged on the inner side wall of the outer frame. The scanning unit is fixedly arranged at one end of the sliding unit close to the sample holder. The drive unit drives the sliding unit to push the scanning unit to advance or withdraw the needle along the length direction of the outer frame.

[0008] Preferably, the driving unit includes an elastic member and a piezoelectric body, and the elastic member and the piezoelectric body each include a fixed end and a movable end. The fixed end of the piezoelectric body is fixedly arranged on the inner wall of the outer frame, and the fixed end of the elastic member is fixedly connected to the movable end of the piezoelectric body. The movable end of the elastic member drives the sliding unit to slide along the length direction of the outer frame.

[0009] Preferably, the sliding unit includes a movable slider and a fixed slider, the fixed slider is fixedly arranged on the side wall inside the outer frame, the movable slider and the fixed slider are slidingly engaged along the length direction of the outer frame, and the movable end of the elastic member drives the movable slider to slide along the length direction of the outer frame; the end of the movable slider close to the sample holder is recorded as the first end, and the end of the movable slider away from the sample holder is recorded as the second end, and the scanning unit is fixedly arranged on the first end of the movable slider.

[0010] Preferably, the scanning unit includes a piezoelectric scanning tube and a probe holder, one end of the piezoelectric scanning tube is fixed to the first end of the movable slider, and the other end of the piezoelectric scanning tube is fixedly connected to the probe holder, and a probe is placed on the probe holder.

[0011] Preferably, the piezoelectric body also includes a first limit block, and the movable slider also includes a second limit block, the second limit block is fixedly set on the second end of the movable slider, and the first limit block is fixedly set at the fixed end of the piezoelectric body and at a position opposite to the second limit block.

[0012] Preferably, the distance d between the second end of the movable slider and the active end of the piezoelectric body is greater than 0.

[0013] Preferably, the outer frame is provided with an opening at one end of the piezoelectric body, and a window is provided on a side wall of the outer frame.

[0014] Preferably, the outer frame is provided with one end of the piezoelectric body at the bottom, and the outer frame is provided with one end of the sample holder at the top; the piezoelectric body is below the movable slider.

[0015] The present invention also provides a scanning imaging method for stable imaging, using a scanning tunneling microscope for stable imaging as described above, comprising the following steps:

[0016] S1: The piezoelectric element receives a needle-advancement signal from the signal acquisition and drive module. After the movable end of the elastic element and the movable slider come into contact with each other, the piezoelectric element drives the scanning unit to advance the needle through the elastic element and the sliding unit. The needle-advancement process includes n consecutive needle-advancement cycles. When the signal acquisition and drive module detects a tunneling current, the scanning unit stops advancing the needle and begins scanning imaging. Where 0 < n, one needle-advancement cycle includes, in chronological order, a needle-advancement approach phase and a needle-advancement hold phase.

[0017] S2, the piezoelectric scanning tube drives the probe holder to move in the XY plane, and the probe scans and images the sample surface;

[0018] S3, scanning imaging is completed, the piezoelectric body receives the needle withdrawal signal sent by the signal acquisition and driving module, and drives the scanning unit to withdraw the needle through the sliding unit.

[0019] Preferably, in S1, the needle approach phase further includes the following:

[0020] The piezoelectric body's movable end extends along the length of the outer frame, while the elastic member, movable slider, and scanning unit remain relatively stationary. Furthermore, the elastic member, movable slider, and scanning unit slide vertically upward at a uniform speed relative to the fixed slider as the piezoelectric body's movable end extends. When the piezoelectric body's movable end extends a first set length L1 in the vertical direction, the piezoelectric body's movable end stops extending, and the needle approach phase of the current needle insertion cycle ends, and the needle insertion holding phase of the current needle insertion cycle begins.

[0021] In S1, the needle holding phase also includes the following:

[0022] The movable end of the piezoelectric body reduces the positive pressure applied to the movable slider by the movable end of the elastic member, and at the same time, the movable end of the piezoelectric body swings and retracts toward the fixed end of the piezoelectric body, driving the movable end of the elastic member to slide and retract toward the fixed end of the piezoelectric body on the outer wall of the movable slider. The movable end of the elastic member slides vertically downward relative to the movable slider in the vertical direction. There is sliding friction between the movable end of the elastic member and the movable slider, and the movable slider, the fixed slider and the scanning unit remain relatively stationary in the vertical direction. There is static friction between the movable slider and the fixed slider. When the movable end of the piezoelectric body shortens the first set length L1 in the vertical direction, the movable end of the piezoelectric body stops retracting, the needle holding phase of the current needle insertion cycle ends, and the needle approach phase of the next needle insertion cycle begins.

[0023] In S3, needle withdrawal specifically includes the following:

[0024] The movable end of the piezoelectric body reduces the positive pressure applied to the movable slider through the movable end of the elastic member. At the same time, the movable end of the piezoelectric body swings and retracts toward the fixed end of the piezoelectric body, driving the movable end of the elastic member to slide and retract toward the fixed end of the piezoelectric body on the outer wall of the movable slider. The movable slider slides vertically downward relative to the fixed slider in the vertical direction to retract the needle of the scanning unit.

[0025] The beneficial effects of the present invention are:

[0026] (1) In the scanning tunneling microscope of the present invention, the driving unit indirectly drives the scanning unit to advance or retract the needle through the sliding unit; because the sliding unit cannot move in the XY plane and can only slide in the Z-axis direction (i.e., the vertical direction in this embodiment), the sliding unit will not introduce interference to the scanning unit in the XY plane, so that the needle entry path and the needle retraction path of the probe remain consistent, ensuring that the probe always points to the same position of the sample during multiple repeated needle insertions without causing offset or tilt on the sample plane. The probe positioning accuracy is high, which further improves the efficiency of scanning imaging.

[0027] (2) In the scanning tunneling microscope of the present invention, the interference amplitude transmitted from the active end of the piezoelectric body to the scanning unit on the Z axis is greatly reduced, the stability of the needle-like tunnel junction is enhanced, the quality and stability of the scanning imaging are improved, the occurrence of needle collision is avoided as much as possible, the service life of the probe is extended, and the sample is prevented from being damaged.

[0028] (3) Different from the inertial force driving method corresponding to the rigid connection between the piezoelectric body and the scanning unit in the prior art, the mirror body of the present invention adopts the elastic extrusion contact and friction force driving method, which not only avoids the rapid change of acceleration caused by the inertial force driving the scanning unit, but also further avoids the vibration of the mirror body components caused by the inertial force driving, that is, reduces the interference generated / coupled at the active end of the piezoelectric body.

[0029] (4) In the prior art, most of the mirror bodies use two piezoelectric bodies that are arranged opposite to each other, one for completing the needle insertion and the other for completing the needle withdrawal. A single piezoelectric body can only move in one direction and cannot move in the opposite direction. The control signal of the two piezoelectric bodies is twice that of the single piezoelectric body design. Not only does it make the entire mirror body larger and more complex to control, but the inertial force driving method also increases the interference inside the mirror body, resulting in poor scanning imaging quality and unstable imaging, and even increases the probability of needle collision. Compared with the prior art, the present invention uses only a single piezoelectric body to complete the needle insertion and needle withdrawal respectively. Not only does it have fewer control signals and simpler control, but it also reduces the cost of a piezoelectric body and saves the space reserved for the expansion and contraction of a piezoelectric body. The structure inside the mirror body is more compact, which improves the space utilization rate inside the mirror body and reduces the size of the mirror body. It is particularly suitable for microscopic imaging measurements in small sample cavities under strong magnetic fields and strong vibration conditions.

[0030] (5) The outer frame and other components in the scope of the present invention are made of single-crystal alumina crystal, which completely avoids the generation of eddy currents during the scanning process, has a small thermal expansion coefficient, small temperature drift, and small temperature changes. Large temperature changes will cause thermal expansion and contraction of components in the scope, further increasing mechanical vibrations. Therefore, the present invention uses single-crystal alumina crystal to make most of the components in the scope, which can also effectively suppress the mechanical vibrations in the scope.

[0031] (6) In the prior art, in the mirror body that adopts the inertial force driving mode, under room temperature conditions, the starting voltage of the piezoelectric body is relatively large, and the piezoelectric coefficient of the piezoelectric body is also relatively large. The required starting voltage is still within the output voltage range of the signal acquisition and driving module; however, under low temperature conditions, the piezoelectric coefficient of the piezoelectric body is reduced by at least 10 times, and the starting voltage of the piezoelectric body is also at least 10 times that under room temperature. This causes the starting voltage of the piezoelectric body to exceed the output range of the signal acquisition and driving module, and the signal acquisition and driving module cannot drive the piezoelectric body to expand and contract. This directly causes the scanning tunneling microscope of the prior art to be unable to scan and image under low temperature conditions. In the present invention, the piezoelectric body drives the scanning unit 5 by indirectly adopting elastic extrusion contact and friction driving. The temperature has little effect on the friction force, and the friction force changes little in a wide temperature range. Therefore, the starting voltage of the piezoelectric body in the present invention is low, the applicable temperature range is wide, and the interference of temperature on whether imaging is performed is small. That is, the scanning tunneling microscope of the present invention is particularly suitable for scanning and imaging at low temperatures.

[0032] (7) The scanning imaging method of a scanning tunneling microscope with stable imaging of the present invention can greatly reduce the interference in the scanning tunneling microscope body, improve the quality and stability of imaging, and avoid pin collision as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1A top view of a scanning tunneling microscope with stable imaging according to the present invention;

[0034] Figure 2 A front view of a scanning tunneling microscope with stable imaging according to the present invention;

[0035] Figure 3 This is a first front cross-sectional view of a mirror body of a scanning tunneling microscope with stable imaging according to the present invention;

[0036] Figure 4 A bottom view of a first mirror body of a scanning tunneling microscope with stable imaging;

[0037] Figure 5 This is a schematic diagram of the first motion state within the scope during the needle insertion process;

[0038] Figure 6 This is a schematic diagram of the second motion state within the scope during the needle insertion process;

[0039] Figure 7 This is a schematic diagram of the third motion state within the scope during the needle insertion process;

[0040] Figure 8 This is a schematic diagram of the fourth motion state within the scope during the needle insertion process;

[0041] Figure 9 This is a schematic diagram of the first motion state within the scope during the needle withdrawal process;

[0042] Figure 10 This is a schematic diagram of the second motion state within the scope during the needle withdrawal process;

[0043] Figure 11 This is a second front cross-sectional view of a mirror body of a scanning tunneling microscope with stable imaging according to the present invention;

[0044] Figure 12 A bottom view of a second mirror body of a scanning tunneling microscope for stable imaging;

[0045] Figure 13 This is a third front cross-sectional view of the mirror body of a scanning tunneling microscope with stable imaging according to the present invention;

[0046] Figure 14 A bottom view of the third mirror body of a scanning tunneling microscope with stable imaging;

[0047] Figure 15 Imaging existing technology scanning tunneling microscope;

[0048] Figure 16 This is imaging of the scanning tunneling microscope of the present invention.

[0049] The actual correspondence between the reference numerals and component names of the present invention is as follows:

[0050] 1. External frame;

[0051] 2. Driving unit; 21. Elastic member; 22. Piezoelectric element; 221. First limiting block;

[0052] 3. Sliding unit; 31. Moving slider; 311. Second limit block; 32. Fixed slider;

[0053] 4. Sample rack;

[0054] 5. Scanning unit; 51. Probe holder; 52. Piezoelectric scanning tube. DETAILED DESCRIPTION

[0055] Any equivalent replacement of the technical features of the technical solution of the present invention and any solution derived by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0056] Example 1

[0057] A scanning tunneling microscope (STM) with stable imaging includes a microscope body, a signal acquisition and drive module, and a computer. The microscope body is electrically connected to the signal acquisition and drive module, which is in turn electrically connected to the computer. The main innovation of the present invention lies in the microscope body, which is not shown in the accompanying drawings.

[0058] The mirror structure of the scanning tunneling microscope of this embodiment is as follows Figures 1 to 4 As shown, the apparatus comprises an outer frame 1, a drive unit 2, a sliding unit 3, a sample holder 4, and a scanning unit 5. The outer frame 1 is a hollow structure. The drive unit 2 and sample holder 4 are located at opposite ends of the outer frame 1. The sliding unit 3 is located on the side wall of the outer frame 1, with one end of the sliding unit 3 close to the drive unit 2 and the other close to the sample holder 4. The scanning unit 5 is fixed to the end of the sliding unit 3 close to the sample holder 4. A computer controls the drive unit 2 through the signal acquisition and drive module, which drives the sliding unit 3 and scanning unit 5 to advance and retract the needle along the length of the outer frame 1.

[0059] For ease of description, in this embodiment, the length direction of the outer frame 1 is the same as the vertical direction, the sample holder 4 is at the top, and the driving unit 2 is at the bottom.

[0060] The drive unit 2 includes an elastic member 21 and a piezoelectric member 22. The piezoelectric member 22 has a fixed end and a movable end. The fixed end of the piezoelectric member 22 is fixed to the inner wall of one end of the outer frame 1. The piezoelectric member 22 has a built-in piezoelectric motor (not shown). The movable end of the piezoelectric member 22 is driven by the piezoelectric motor to extend or contract along the length of the outer frame 1. The movable end of the piezoelectric member 22 can also swing around the fixed end of the piezoelectric member 22 as the center of the circle under the drive of the piezoelectric motor. The elastic member 21 has a fixed end and a movable end. The fixed end of the elastic member 21 is fixedly connected to the movable end of the piezoelectric member 22.

[0061] The sliding unit 3 includes a movable slider 31 and a fixed slider 32. The fixed slider 32 is fixedly arranged on the side wall inside the outer frame 1. The movable slider 31 and the fixed slider 32 are slidingly engaged with each other. The movable slider 31 can slide relative to the fixed slider 32 along the length direction of the outer frame 1, but the movable slider 31 cannot rotate circumferentially.

[0062] like Figure 3 and Figure 4 As shown, in this embodiment, a guide groove is provided on the fixed slider 32 along the length of the outer frame 1, and a guide rail is provided on the movable slider 31 to match the guide groove. The guide rail on the movable slider 31 engages with the guide groove on the fixed slider 32. Of course, the reverse arrangement is also possible in the present invention, whereby a guide rail is provided on the fixed slider 32 along the length of the outer frame 1, and a guide groove is provided on the movable slider 31 to match the guide groove. The guide rail on the fixed slider 32 engages with the guide groove on the movable slider 31. The end of the movable slider 31 closest to the sample holder 4 is designated as the first end, and the end of the movable slider 31 away from the sample holder 4 is designated as the second end. The scanning unit 5 is fixedly mounted on the first end of the movable slider 31.

[0063] Optionally, the piezoelectric body 22 also includes a first limit block 221, and the movable slider 31 also includes a second limit block 311. The first limit block 221 is protruded from the fixed end of the piezoelectric body 22 toward the movable slider 31, and the second limit block 311 is set on the second end of the movable slider 31. When the first limit block 221 contacts the second limit block 311, the distance d between the second end of the movable slider 31 and the movable end of the piezoelectric body 22 is greater than 0.

[0064] The scanning unit 5 includes a piezoelectric scanning tube 52 and a probe holder 51. One end of the piezoelectric scanning tube 52 is fixed to the first end of the movable slider 31, and the other end is fixedly connected to the probe holder 51. The probe holder 51 is used to place probes, the specific probes of which are determined by the sample and imaging requirements. The piezoelectric scanning tube 52 in the present invention is an XY piezoelectric scanning tube.

[0065] Driven by the piezoelectric element 22, the movable end of the elastic member 21 can contact or disengage the movable slider 31. When the movable end of the elastic member 21 contacts the movable slider 31, the movable end of the elastic member 21 and the movable slider 31 may be in point contact or surface contact. The form of contact between the movable end of the elastic member 21 and the movable slider 31 is not a limitation of the present invention. The contact point / contact surface when the movable end of the elastic member 21 contacts the movable slider 31 is defined as the elastic member contact portion; the contact point / contact surface when the movable slider 31 contacts the movable end of the elastic member 21 is defined as the movable slider contact portion.

[0066] One end of the outer frame 1 where the sample holder 4 is provided is closed, which is referred to as the closed end of the outer frame 1 . The sample holder 4 is fixed to the closed end of the outer frame 1 and is used to place samples. The end of the outer frame 1 where the driving unit 2 is provided can be closed or open.

[0067] Optionally, a window (not shown) is provided on the side wall of the outer frame 1 .

[0068] The outer frame 1 is provided with an opening at one end of the driving unit 2, and / or a window is provided on the side wall of the outer frame 1, which not only facilitates the replacement of probes or samples, but also facilitates the repair and replacement of other components in the scope, thereby improving the scanning imaging efficiency of the scanning tunneling microscope.

[0069] In this embodiment, the outer frame 1 is provided with an opening at one end of the driving unit 2 , and the outer frame 1 is cylindrical.

[0070] Optionally, the outer frame 1 is in the shape of a square column. The specific shape of the outer frame 1 is not intended to limit the present invention.

[0071] In this embodiment, the vertical height of the contact portion of the elastic member is lower than the vertical height of the first end of the movable slider 31 , thereby ensuring that the elastic member 21 can contact the movable slider 31 under the drive of the piezoelectric body 22 .

[0072] The positional relationship and relative motion state between the elastic member 21, the movable slider 31 and the fixed slider 32 are as follows: Figures 3 to 14 As shown in the figure, the green arrow represents the movement direction of the active end of the piezoelectric body 22, the green arrow represents the movement direction of the active end of the elastic member 21, and the purple arrow represents the movement direction of the movable slider 31 and the scanning unit 5.

[0073] The needle advancement process is the process in which the scanning unit 5 continuously approaches the sample holder 4 in the vertical direction. The needle advancement process includes n consecutive needle advancement cycles, 0<n, until the probe enters the tunnel area, and the signal acquisition and driving module detects the tunnel current. At this time, the needle advancement process ends and enters the scanning imaging process; when the probe enters the tunnel area, the probe and the sample surface still maintain a certain distance; in the scanning imaging process, the piezoelectric scanning tube 52 drives the probe holder 51 to move in the XY plane, that is, the probe on the probe holder 51 scans and images the sample surface on the sample holder 4. After the scanning imaging process is completed, the needle withdrawal process begins; the needle withdrawal process is the process in which the scanning unit 5 moves away from the sample holder 4 in the vertical direction.

[0074] Optionally, the outer frame 1, the first limit block 221, the second limit block 311, and the fixed slider 32 are all made of single-crystal alumina. Single-crystal alumina has extremely high anti-magnetism and is compatible with strong magnetic field environments above 30 Tesla. It has excellent insulation properties, completely avoids the generation of eddy currents during the scanning process, and completely eliminates the interference of eddy currents caused by scanning on the scanning imaging. It is compatible with strong magnetic fields, has a small thermal expansion coefficient, and has a small temperature drift, which significantly reduces temperature drift during long-term scanning. It has excellent low-temperature compatibility and can obtain low-temperature scanning data.

[0075] The following describes in detail the positional relationship in the scope and the probe insertion process, scanning imaging process, and needle withdrawal process:

[0076] The red arrow represents the motion state of the elastic member 21 , the green arrow represents the motion state of the free end of the piezoelectric body 22 , and the purple arrow represents the motion state of the movable slider 31 .

[0077] The first position relationship in the mirror body: the piezoelectric body 22 is below the movable slider 31, and the horizontal projection of the piezoelectric body 22 intersects with the horizontal projection of the movable slider 31: The position relationship of each component in the mirror body is as follows: Figures 3 and 4 As shown, Figure 4 and Figure 3 Correspondingly, the piezoelectric body 22 includes a first limiting block 221 , and the movable slider 31 includes a second limiting block 311 .

[0078] 1. Needle insertion process

[0079] After the piezoelectric body 22 receives the needle insertion signal sent by the signal acquisition and driving module, the movable end of the piezoelectric body 22 rotates toward the movable slider 31 until the movable end of the elastic member 21 is squeezed and contacted with the movable slider 31, starting the needle insertion approach phase of the current needle insertion cycle.

[0080] A needle insertion cycle includes the needle insertion approach phase and the needle insertion holding phase in chronological order:

[0081] (1) Needle approach phase

[0082] During the needle approaching stage, the movable end of the piezoelectric body 22 extends toward the sample holder 4. During this process, the contact position between the movable slider 31 and the movable end of the elastic member 21 remains unchanged. The movable slider 31 is driven by the movable end of the elastic member 21 to slide toward the sample holder 4 at a constant speed relative to the fixed slider 32. The probe gradually approaches the sample on the sample holder 4. Figures 5 to 7 As shown, when the needle approaching phase of the current needle insertion cycle ends, the probe stops approaching the sample on the sample rack 4 and then enters the needle holding phase of the current needle insertion cycle.

[0083] During the needle approach stage, if the signal acquisition and drive module detects the tunnel current, the computer sends a stop needle insertion signal to the piezoelectric body 22 through the signal acquisition and drive module. At this time, the piezoelectric body 22 stops moving, the needle approach stage of the current needle insertion cycle ends, and the entire needle insertion process ends. The probe holder 51 no longer approaches the sample on the sample holder 4 and enters the scanning imaging process.

[0084] In the same needle insertion cycle, at the end of the needle insertion approach phase, the active end of the piezoelectric body 22 is extended by the first set length L1 compared to the beginning of the needle insertion approach phase; at the end of the needle insertion approach phase, the extended length of the active end of the piezoelectric body 22 is less than the first set length L1 compared to the beginning of the needle insertion approach phase.

[0085] Force analysis during the needle approach phase: The movable slider 31 and the scanning unit 5 are considered as a whole, and the total gravity of the whole is recorded as G; when the movable end of the elastic member 21 is not in contact with the movable slider 31, the maximum static friction and sliding friction on the contact surface between the movable slider 31 and the fixed slider 32 are recorded as f S1,MAX and f K1 , and G>f S1,MAX >f K1 >0, so the movable slider 31 will slide vertically downward relative to the fixed slider 32 until the first limit block 221 contacts the second limit block 311, at which point the movable slider 31 stops sliding vertically downward. At this time, the distance d between the second end of the movable slider 31 and the movable end of the piezoelectric element 22 is >0. When the movable end of the elastic member 21 is in compression contact with the movable slider 31, the movable slider 31 and the fixed slider 32 are also in compression contact. At this time, the maximum static friction and sliding friction on the contact surface between the movable slider 31 and the fixed slider 32 are recorded as f, respectively. S1,MAX ′ and f K1 ′, the static friction force and the maximum static friction force between the movable end of the elastic member 21 and the movable slider 31 are respectively recorded as f S2 and f S2,MAX Because the movable end of the elastic member 21 exerts a positive pressure on the contact portion of the movable slider, the movable slider 31 also exerts a positive pressure on the engagement contact surface of the fixed slider 32, so there is f S1,MAX ′>f S1,MAX>0 and f K1 ′>f K1 >0.

[0086] When the active end of the piezoelectric body 22 extends toward the sample holder 4, Figures 5 and 6 As shown in FIG. 1 , the contact portion between the movable slider 31 and the movable end of the elastic member 21 remains unchanged, but the fixed end of the elastic member 21 moves vertically upward as the movable end of the piezoelectric body 22 stretches. As the elastic member 21 deforms, the angle θ between the contact portion of the elastic member 21 and the movable slider also changes, and the positive pressure exerted by the movable end of the elastic member 21 on the contact portion of the movable slider also increases, i.e., f S1,MAX ′、f K1 ′、f S2,MAX and f S2 When f S2 Increase to 0<f S2 =(G+f S1,MAX ′)<f S2,MAX When the movable end of the elastic member 21 and the movable slider 31 remain relatively stationary, the movable slider 31 begins to slide vertically upward relative to the fixed slider 32. During this process, the elastic member 21 is deformed again, so that the angle θ between the contact portion of the elastic member 21 and the movable slider also changes. The positive pressure exerted by the movable end of the elastic member 21 on the contact portion of the movable slider also decreases until 0<f is satisfied. S2 =(G+f K1 ′)<f S2,MAX When , the elastic member 21 no longer deforms, the angle θ no longer changes, and the positive pressure exerted by the movable end of the elastic member 21 on the contact portion of the movable slider no longer decreases. At this time, the elastic member 21, the movable slider 31 and the scanning unit 5 remain relatively stationary, and as the movable end of the piezoelectric body 22 extends, they slide vertically upward at a uniform speed relative to the fixed slider 32.

[0087] (2) Needle insertion and maintenance phase

[0088] like Figure 8 As shown, during the needle insertion and holding stage: the movable end of the piezoelectric body 22 swings and retracts toward the fixed end of the piezoelectric body 22, and the movable end of the piezoelectric body 22 reduces the positive pressure applied to the movable slider 31 by the movable end of the elastic member 21, driving the movable end of the elastic member 21 to slide and retract on the outer wall of the movable slider 31 toward the fixed end of the piezoelectric body 22, and making the movable slider 31 and the fixed slider 32 remain relatively stationary in the vertical direction. The movable end of the elastic member 21 slides vertically downward relative to the movable slider 31 in the vertical direction. The static friction force on the contact surface between the movable slider 31 and the fixed slider 32 at this time is recorded as f S1 The vertical component of the sliding friction force on the contact surface between the movable end of the elastic member 21 and the movable slider 32 is f K2 *, then f is satisfied S1 ″=G+fK2 *, until the current needle insertion holding phase ends, the current needle insertion cycle ends and the needle insertion approach phase of the next needle insertion cycle is entered again.

[0089] It should be emphasized that: at the beginning of the needle insertion and holding stage, the contact point between the movable end of the elastic member 21 and the movable slider 31 remains unchanged, but the elastic member 21 is deformed, and the positive pressure exerted by the movable end of the elastic member 21 on the contact point of the movable slider is reduced; when the movable end of the elastic member 21 slides on the outer wall of the movable slider 31, the elastic member 21 no longer deforms.

[0090] In the same needle insertion cycle, at the end of the needle insertion and holding phase, the movable end of the piezoelectric body 22 is shortened by a first set length L1 in the vertical direction compared to the beginning of the needle insertion and holding phase.

[0091] At the end of one needle insertion cycle, the movable end of the piezoelectric body 22 remains in a constant position in the vertical direction, while the movable slider 31 rises a step length SP in the vertical direction, where 0<SP≤L1.

[0092] During the entire needle insertion process, the movable slider 31 rises n steps in the vertical direction, and the probe gradually approaches the tunnel area. The probe tip entering the tunnel area can only occur during the needle insertion approach phase, not during the needle insertion holding phase.

[0093] 2. Scanning imaging process

[0094] In the vertical direction, the force analysis at the end of the needle approach phase is the same as the force analysis during the scanning imaging process: that is, the movable slider 31, the fixed slider 32 and the elastic member 21 remain relatively stationary in the vertical direction, and the movable end of the elastic member 21 is in compression contact with the movable slider 31, and the movable slider 31 is in compression contact with the fixed slider 32. The static friction force on the contact surface between the movable end of the elastic member 21 and the movable slider 31 at this time is recorded as f S1 ′, the static friction force on the contact surface between the movable slider 31 and the fixed slider 32 is recorded as f S2 ′, then (f S1 ′+f S2 ′)=G.

[0095] 3. Needle withdrawal process

[0096] When the scanning imaging process is finished, the piezoelectric body 22 receives the needle withdrawal signal sent by the signal acquisition and driving module, such as Figure 9As shown, this is a needle withdrawal method in which the elastic member 21 is in contact with the movable slider 31: the movable end of the piezoelectric body 22 reduces the positive pressure applied to the movable slider 31 by the movable end of the elastic member 21, and at the same time, the movable end of the piezoelectric body 22 swings and retracts toward the fixed end of the piezoelectric body 22, driving the movable end of the elastic member 21 to slide and retract toward the fixed end of the piezoelectric body 22 on the outer wall of the movable slider 31, and causing the movable slider 31 to slide vertically downward relative to the fixed slider 32. During this process, the movable slider 31 also slides vertically downward relative to the movable end of the elastic member 21 until the first limit block 221 contacts the second limit block 311, the movable slider 31 stops sliding vertically downward, and the needle withdrawal process ends. At this time, the distance d between the second end of the movable slider 31 and the movable end of the piezoelectric body 22 is greater than 0.

[0097] It should be emphasized that: at the beginning of the needle withdrawal method with contact, the contact point between the movable end of the elastic member 21 and the movable slider 31 remains unchanged, but the elastic member 21 is deformed, and the positive pressure exerted by the movable end of the elastic member 21 on the contact point of the movable slider is reduced; when the movable end of the elastic member 21 slides on the outer wall of the movable slider 31, the elastic member 21 no longer deforms.

[0098] In the contact needle withdrawal method, the entire sliding movement of the movable slider 31 is controlled by the elastic member 21, that is, the sliding speed of the movable slider 31 and the sliding distance of the movable slider 31 are all controlled by the elastic member 21, which makes the needle withdrawal process smoother; and the sliding distance of the movable slider 31 in this needle withdrawal method is controllable, so each needle withdrawal does not have to wait until the first limit block 221 contacts the second limit block 311 before stopping. The technician can control the sliding distance of the movable slider 31 when withdrawing the needle according to the probe / sample characteristics of the next scanning imaging, that is, timely increase the positive pressure applied by the active end of the piezoelectric body 22 to the movable slider 31 through the active end of the elastic member 21 to stop the sliding of the movable slider 31, thereby reducing the total time of the needle insertion process in the next scanning imaging and improving the efficiency of the next scanning imaging. Furthermore, the presence of the first limit block 221 and the second limit block 311 limits the downward movement of the movable slider 31, that is, the movable slider 31 cannot slide down indefinitely, and can only slide down to the moment when the first limit block 221 contacts the second limit block 311. Therefore, even if one end of the outer frame 1 where the driving unit 2 is located is open, the movable slider 31 will not slide out of the mirror body.

[0099] Optional, such as Figure 10As shown, this is a needle retraction method without contact between the elastic member 21 and the movable slider 31: the movable end of the piezoelectric body 22 rotates in the direction away from the movable slider 31, and at the same time, the movable end of the piezoelectric body 22 retracts toward the fixed end of the piezoelectric body 22, so that there is no contact between the movable end of the elastic member 21 and the movable slider 31, and the whole formed by the movable slider 31 and the scanning unit 5 slides down under the action of gravity until the first limit block 221 contacts the second limit block 311, and the movable slider 31 stops sliding vertically downward, and the needle retraction process ends. At this time, the distance d between the second end of the movable slider 31 and the movable end of the piezoelectric body 22 is greater than 0.

[0100] In the contactless needle withdrawal method, there is no contact between the movable end of the elastic member 21 and the movable slider 31, and the entire needle withdrawal process is not controlled by the elastic member 21. The control signal received by the piezoelectric body 22 during the needle withdrawal process is simple; compared with the contact needle withdrawal method, the movable slider 31 slides down the same distance, and the contactless needle withdrawal method takes less time; at the same time, the presence of the first limit block 221 and the second limit block 311 limits the downward movement of the movable slider 31, ensuring that each needle withdrawal is completed when the first limit block 221 contacts the second limit block 311, and even if one end of the outer frame 1 where the drive unit 2 is located is open, the movable slider 31 will not slide out of the mirror body.

[0101] The second position relationship in the mirror body: the piezoelectric body 22 is below the movable slider 31 and the fixed slider 32, and the horizontal projection of the piezoelectric body 22 intersects with the horizontal projection of the movable slider 31 and the fixed slider 32: The position relationship of each component in the mirror body is as follows Figures 11 and 12 As shown, Figure 12 and Figure 11 Correspondingly, the piezoelectric body 22 does not include the first limiting block 221 , and the movable slider 31 does not include the second limiting block 311 .

[0102] The scanning and imaging process of the second position relationship within the scope is the same as the scanning and imaging process of the first position relationship within the scope.

[0103] The needle withdrawal process of the second position relationship in the mirror body is a needle withdrawal method in which the elastic member 21 is in contact with the movable slider 31: the movable end of the piezoelectric body 22 swings and retracts toward the fixed end of the piezoelectric body 22, driving the movable end of the elastic member 21 to slide and retract on the outer wall of the movable slider 31 toward the fixed end of the piezoelectric body 22, and causing the movable slider 31 to slide vertically downward relative to the fixed slider 32. During this process, the movable slider 31 also slides vertically downward relative to the movable end of the elastic member 21 until the movable end of the piezoelectric body 22 retracts to the set length L1 of the piezoelectric body. The movable end of the piezoelectric body 22 rotates toward the movable slider 31, and the positive pressure exerted by the movable end of the elastic member 21 on the contact part of the movable slider increases, so that the elastic member 21, the movable slider 31 and the scanning unit 5 remain relatively stationary in the vertical direction, and the needle withdrawal process ends.

[0104] The needle insertion process in the second position relationship within the scope is basically the same as the needle insertion process in the first position relationship within the scope. The difference is that: because the needle withdrawal process in the second position relationship within the scope is a contact needle withdrawal method, that is, the movable end of the elastic member 21 is always in contact with the movable slider 31, so after the piezoelectric body 22 receives the needle insertion signal sent by the signal acquisition and drive module, the movable end of the piezoelectric body 22 can directly extend toward the sample holder 4. The subsequent needle insertion process is the same as the needle insertion process in the first position relationship, and will not be repeated here.

[0105] The second position relationship in the mirror body does not adopt the needle withdrawal method using the elastic member 21 and the movable slider 31 without contact, the reason is: Figure 11 As shown, the horizontal projection of the piezoelectric element 22 intersects with the horizontal projections of the movable slider 31 and the fixed slider 32. During the needle withdrawal process, if there is no contact between the movable end of the elastic member 21 and the movable slider 31, the movable slider 31 and the scanning unit 5 will slide downward under the action of gravity. During the entire sliding process, the sliding speed and the sliding stop position are completely uncontrolled by the elastic member 21. Only when the second end of the movable slider 31 contacts the movable end of the piezoelectric element 22 will the movable slider 31 stop sliding. However, when a new experiment requires needle insertion, the mechanical vibration generated by the movable end of the piezoelectric element 22 is directly transmitted to the movable slider 31 through rigid contact with the movable slider 31. A major reason for the poor imaging quality in the prior art is that the piezoelectric element drives the scanning unit to advance the needle through rigid contact, which is undesirable in the present invention. Therefore, when the second position relationship is achieved within the scope, a contact needle withdrawal method is adopted within the scope to ensure that the movable end of the piezoelectric element 22 does not make rigid contact with the movable slider 31.

[0106] From the above analysis, it can be seen that in the second position relationship in the mirror body, it is useless even if the second end of the movable slider 31 is provided with a second limit block 311, because the second limit block 311 cannot contact the movable end of the piezoelectric body 22, and naturally cannot play the role of limiting the position in the vertical direction. Naturally, even if the corresponding first limit block 221 on the piezoelectric body 22 exists, it has no effect.

[0107] The third position relationship in the mirror body: the piezoelectric body 22 is below the movable slider 31, and the horizontal projection of the piezoelectric body 22 does not intersect with the horizontal projection of the movable slider 31: The position relationship of each component in the mirror body is as follows Figures 13 and 14 As shown, Figure 14 and Figure 13 Correspondingly, the piezoelectric body 22 does not include the first limiting block 221 , and the movable slider 31 does not include the second limiting block 311 .

[0108] The needle insertion process, scanning imaging process and needle withdrawal process of the third position relationship within the scope are the same as those of the second position relationship within the scope.

[0109] The third position relationship in the scope does not adopt the needle withdrawal method in which the elastic member 21 and the movable slider 31 are not in contact. The reason is the same as that of the second position relationship in the scope, which will not be repeated here. The third position relationship in the scope adopts the needle withdrawal method in which the elastic member 21 and the movable slider 31 are in contact.

[0110] In the scanning tunneling microscope of the present invention, no matter which positional relationship is used within the microscope body, the interference during the scanning experiment can be greatly reduced. The following is a detailed analysis:

[0111] Firstly, no matter in which process, as long as the piezoelectric body 22 moves, there is no rigid contact between the movable slider 31 and the active end of the piezoelectric body 22. Naturally, all interference generated by the active end of the piezoelectric body 22 cannot be directly transmitted to the movable slider 31 through rigid contact.

[0112] During the needle approach phase, there is a static friction force f between the contact surface of the elastic member 21 and the movable slider 31. S2 There is a static friction force f between the movable slider 31 and the fixed slider 32 S1 , the elastic member 21, the movable slider 31, the fixed slider 32 and the scanning unit 5 do not slide relative to each other in the vertical direction; as the piezoelectric body 22 stretches, the contact portion between the movable end of the elastic member 21 and the movable slider 31 remains unchanged, which will cause the elastic member 21 to deform, and the kinetic energy E of the piezoelectric body 22 K1 Converted into the elastic potential energy E of the elastic member 21 P1 The elastic member 21 also increases the positive pressure applied to the movable slider 31 by its own deformation, thereby increasing the vertical upward static friction force f acting on the movable slider 31 by the movable end of the elastic member 21. S2 , further ensuring that the contact position between the movable end of the elastic member 21 and the movable slider 31 remains unchanged; when the elastic member 21 is deformed to 0<f S2 =(G+f K1 ′)<f S2,MAX When the elastic member 21 no longer deforms, the elastic potential energy E P1 The elastic potential energy stored in the elastic member 21 at this time is recorded as the upper limit of the elastic potential energy E P1，MAX Kinetic energy E of piezoelectric body 22 K1 Still continuously converted into elastic potential energy E P1 , the elastic member 21 will exceed the upper limit of elastic potential energy E P1，MAX Excess elastic potential energy △E P1 Converted into kinetic energy E of the elastic member 21, the movable slider 31 and the scanning unit 5 K2and the internal energy U1 of the movable slider 31 (the movable slider 31 slides vertically upward relative to the fixed slider 32, generating heat through friction). At this time, the elastic member 21, the movable slider 31 and the scanning unit 5 begin to slide vertically upward relative to the fixed slider 32. When the elastic member 21, the movable slider 31 and the scanning unit 5 begin to slide vertically upward relative to the fixed slider 32, the elastic member 21 will deform slightly, causing the elastic potential energy E stored in the elastic member 21 to P1 Simply put, the kinetic energy E of the piezoelectric body 22 K1 First converted into the elastic potential energy E of the elastic member 21 P1 Store until the elastic potential energy reaches the upper limit E P1，MAX When the excess elastic potential energy △E P1 is converted into the kinetic energy E of the whole composed of the elastic member 21, the movable slider 31 and the scanning unit 5 K2 and the internal energy U1 of the moving slider 31; but the static friction force f corresponding to the upper limit of elastic potential energy S2 <f S2,MAX Therefore, no matter when in the needle approaching stage, the kinetic energy generated by the interference at the active end of the piezoelectric body 22 will first be converted into the elastic potential energy E of the elastic member 21. P1 , only when the upper limit of elastic potential energy E is exceeded P1，MAX Elastic potential energy △E P1 It will be converted into kinetic energy E K2 and internal energy U, and because △E P1 Only part of it will be converted into kinetic energy E K2 Therefore, from the perspective of energy conversion, it can be clearly seen that in the present invention, the interference at the active end of the piezoelectric body 22 is greatly weakened after being transmitted to the movable slider 31.

[0113] During the needle insertion and holding phase: the kinetic energy E of the piezoelectric body 22 K1 Converted into the elastic potential energy E of the elastic member 21 P1 , the kinetic energy E of the elastic member 21 P3 and the internal energy U2 of the elastic member 21 (the elastic member 21 slides relative to the movable slider 31, generating frictional heat), while the movable slider 31 is stationary relative to the fixed slider 32 in the vertical direction; therefore, the kinetic energy generated by the interference at the active end of the piezoelectric body 22 will only be converted into the elastic potential energy E of the elastic member 21. P1 , the kinetic energy E of the elastic member 21 P3 As well as the internal energy U2 of the elastic member 21 , the movable slider 31 remains stationary in the vertical direction relative to the fixed slider 32 .

[0114] During the scanning imaging process: the elastic potential energy E stored in the elastic member 21 P1 It does not exceed the upper limit of elastic potential energy E P1，MAX, and the static friction force f acting on the movable slider 31 in the vertical direction by the movable end of the elastic member 21 S2 The static friction force f acting on the movable slider 31 in the vertical direction of the fixed slider 32 is less than the corresponding maximum static friction force. S1 It is also smaller than the corresponding maximum static friction force, so the contact point between the movable end of the elastic member 21 and the movable slider 31 remains unchanged, and the position of the movable slider 31 relative to the fixed slider 32 in the vertical direction remains unchanged. The kinetic energy generated by the interference at the movable end of the piezoelectric body 22 will only be converted into the elastic potential energy E of the elastic member 21. P1 , that is, the elastic member 21 is deformed first; only the interference generated by the active end of the piezoelectric body 22 is too large, exceeding the upper limit of the elastic potential energy E P1，MAX Elastic potential energy △E P1 Only when the movable slider 31 moves vertically upward relative to the fixed slider 32 can the movable slider 31 move vertically upward relative to the fixed slider 32. The energy conversion analysis at this time is the same as that in the "needle approach stage" and will not be repeated here. That is, of the kinetic energy generated by the interference at the active end of the piezoelectric element 22, only a small portion is ultimately converted into the kinetic energy of the movable slider 31. The interference at the active end of the piezoelectric element 22 is significantly reduced in the present invention. In short, during the scanning and imaging process, the small-amplitude interference generated by the active end of the piezoelectric element 22 will not affect the quality of the scanning and imaging; the large-amplitude interference generated by the active end of the piezoelectric element 22 is reduced to a small-amplitude interference on the movable slider 31, thereby minimizing the impact on the scanning and imaging quality.

[0115] During the needle withdrawal process: In the non-contact needle withdrawal method, any interference generated by the active end of the piezoelectric body 22 will not damage the sample surface and the probe tip. In the contact needle withdrawal method, any interference generated by the active end of the piezoelectric body 22 may only cause the sample surface and the probe tip to collide with the needle and cause damage at the beginning of the needle withdrawal; in the subsequent moments, because the scanning unit 5 gradually moves away from the sample, even if the interference of the active end of the piezoelectric body 22 causes the probe tip to advance toward the sample surface, the probe tip will not contact the sample surface. The interference generated by the active end of the piezoelectric body 22 occurs at the beginning of the needle withdrawal. The energy conversion analysis is the same as the "scanning imaging process" and will not be repeated here. That is, at the beginning of the needle withdrawal, if the active end of the piezoelectric body 22 generates a small interference, the movable slider 31 will remain stationary in the vertical direction with the fixed slider 32. If the active end of the piezoelectric body 22 generates a large interference, the movable slider 31 may only advance a very small distance in the vertical direction relative to the fixed slider 32, minimizing the occurrence of the probe tip and the sample surface.

[0116] In the scanning tunneling microscope body of the present invention, the driving unit 2 indirectly drives the scanning unit 5 to advance or retract the needle through the sliding unit 3; because the sliding unit 3 cannot move in the XY plane and can only slide in the Z-axis direction (i.e., the vertical direction in this embodiment), the sliding unit 3 will not introduce interference to the scanning unit 5 in the XY plane, so that the needle advancement path and the needle retraction path of the probe remain consistent, ensuring that the probe always points to the same position of the sample during multiple repeated needle advancements without causing offset or tilt on the sample plane. The probe positioning accuracy is high, which further improves the efficiency of scanning imaging.

[0117] Interference factors such as mechanical vibration, environmental vibration, thermal drift, and thermal fluctuation will only introduce interference in the Z-axis direction to the scanning unit 5 if they occur / couple at the active end of the piezoelectric body 22. From the above analysis, it can be seen that in the mirror body of the present invention, the piezoelectric body 22 in the driving unit 2 is squeezed into contact with the movable slider 31 of the sliding unit 3 through the elastic member 21, and the elastic member 21 drives the movable slider 31 to move along the Z-axis direction through friction. In this process, the interference at the active end of the piezoelectric body 22 is stored as elastic potential energy by the elastic member 21 during the energy conversion process, or is converted into internal energy and finally dissipated in the air. Therefore, if only a small interference occurs at the active end of the piezoelectric body 22, the present invention can completely convert these interferences into potential energy and store them to avoid these interferences from being transmitted to the scanning unit 5. Only when a large interference occurs at the active end of the piezoelectric body 22, only a small part of the energy corresponding to the large interference is actually used to move the scanning unit 5 on the Z-axis. That is, in the scanning tunneling microscope of the present invention, the interference amplitude transmitted from the active end of the piezoelectric body 22 to the scanning unit 5 on the Z axis is greatly reduced, the stability of the needle-like tunnel junction is enhanced, the quality and stability of the scanning imaging are improved, the occurrence of needle collision is avoided as much as possible, the service life of the probe is extended, and the sample is prevented from being damaged.

[0118] Different from the inertial force driving method corresponding to the rigid connection between the piezoelectric body and the scanning unit in the prior art, the mirror body of the present invention adopts elastic extrusion contact and friction force driving method, which not only avoids the rapid change of acceleration caused by the inertial force driving the scanning unit, but also further avoids the vibration of the components in the mirror body caused by the inertial force driving, that is, reduces the interference occurring / coupling at the active end of the piezoelectric body 22.

[0119] In the existing microscope body, most of the existing technologies use two piezoelectric bodies arranged opposite each other, one responsible for completing the needle insertion and the other responsible for completing the needle withdrawal. A single piezoelectric body can only move in one direction and cannot move in the opposite direction. The control signal of the two piezoelectric bodies is twice that of the single piezoelectric body design. Not only does it make the entire microscope body larger and more complex to control, but the inertial force drive method also increases the interference within the microscope body, resulting in poor scanning imaging quality and unstable imaging, and even increases the probability of needle collision. Compared with the existing technology, the present invention only uses a single piezoelectric body to complete the needle insertion and withdrawal respectively. Not only does it have fewer control signals and simpler control, but it also reduces the cost of a single piezoelectric body and saves the space reserved for the expansion and contraction of a piezoelectric body. The structure inside the microscope body is more compact, the space utilization rate inside the microscope body is improved, and the volume of the microscope body is reduced. It is particularly suitable for microscopic imaging measurements in small sample cavities under strong magnetic fields and strong vibration conditions.

[0120] The outer frame and other components in the scope of the present invention are made of single-crystal alumina crystal, which completely avoids the generation of eddy currents during the scanning process, has a small thermal expansion coefficient, small temperature drift, and small temperature changes. Large temperature changes will cause thermal expansion and contraction of components in the scope, further increasing mechanical vibrations. Therefore, the present invention uses single-crystal alumina crystal to make the outer frame and other components in the scope, which can effectively suppress the mechanical vibrations in the scope.

[0121] In conventional mirrors driven by inertial force, at room temperature, the piezoelectric element has a relatively high starting voltage and a relatively large piezoelectric coefficient, requiring a starting voltage that is within the output voltage range of the signal acquisition and drive module. However, at low temperatures, the piezoelectric coefficient decreases by at least 10 times, and the starting voltage of the piezoelectric element is also at least 10 times that of room temperature. This causes the starting voltage of the piezoelectric element to exceed the output range of the signal acquisition and drive module, rendering the module unable to drive the piezoelectric element to expand or contract. This directly results in the inability of conventional scanning tunneling microscopes to scan and image at low temperatures. In the present invention, the piezoelectric element indirectly drives the scanning unit 5 by elastic extrusion contact and frictional force drive. Temperature has little effect on friction, and frictional force varies little over a wide temperature range. Therefore, the starting voltage of the piezoelectric element in the present invention is low, the applicable temperature range is wide, and temperature has little influence on imaging. Therefore, the scanning tunneling microscope of the present invention is particularly suitable for scanning and imaging at low temperatures.

[0122] like Figure 15 The imaging of the existing scanning tunneling microscope is carried out by using two piezoelectric bodies arranged opposite to each other and driven by inertial force. Figure 16The imaging of the scanning tunneling microscope of the present invention shows that the clarity of the imaging of the scanning tunneling microscope of the present invention is significantly higher than that of the imaging of the prior art; and the overall clarity of the imaging of the present invention is similar, that is, the imaging quality of the present invention is relatively stable, while the imaging of the prior art is slightly clearer in some places and very blurry in other places, that is, the imaging quality of the prior art is very unstable.

[0123] Example 2

[0124] The present invention also provides a scanning imaging method for a scanning tunneling microscope with stable imaging, using the scanning tunneling microscope with stable imaging as described in Example 1, comprising the following steps:

[0125] S1: When the piezoelectric element 22 receives the needle-advancing signal from the signal acquisition and driving module, it starts to drive the sliding unit 3 to push the scanning unit 5 to advance the needle. When the signal acquisition and driving module detects the tunneling current, the scanning unit 5 stops advancing the needle and starts scanning imaging.

[0126] S2, the piezoelectric scanning tube 52 drives the probe holder 51 to move in the XY plane, and the probe scans and images the sample surface;

[0127] S3 , when the scanning imaging is finished, the piezoelectric body 22 receives the needle-retracting signal sent by the signal acquisition and driving module, and drives the scanning unit 5 to retract the needle through the sliding unit 3 .

[0128] In S1, when the piezoelectric body 22 receives the needle insertion signal, the movable end of the elastic member 21 is squeezed and contacted with the movable slider 31, and the piezoelectric body 22 drives the scanning unit 5 to advance the needle through the elastic member 21 and the sliding unit 3. The needle insertion process includes n consecutive needle insertion cycles. When the signal acquisition and driving module collects the tunnel current, the scanning unit 5 stops advancing the needle and starts scanning imaging. 0<n, a needle insertion cycle includes a needle insertion approach stage and a needle insertion holding stage in chronological order.

[0129] The needle approach stage also includes the following contents: the movable end of the piezoelectric body 22 extends along the length direction of the outer frame 1, the elastic member 21, the movable slider 31 and the scanning unit 5 remain relatively stationary, and the elastic member 21, the movable slider 31 and the scanning unit 5 slide vertically upward at a uniform speed relative to the fixed slider 32 as the movable end of the piezoelectric body 22 extends; until the movable end of the piezoelectric body 22 extends in the vertical direction by a first set length L1, the movable end of the piezoelectric body 22 stops extending, the needle approach stage of the current needle insertion cycle ends, and the needle insertion holding stage of the current needle insertion cycle begins.

[0130] The needle insertion holding stage also includes the following contents: the movable end of the piezoelectric body 22 reduces the positive pressure applied to the movable slider 31 through the movable end of the elastic member 21, and at the same time the movable end of the piezoelectric body 22 swings and retracts toward the fixed end of the piezoelectric body 22, driving the movable end of the elastic member 21 to slide and retract toward the fixed end of the piezoelectric body 22 on the outer wall of the movable slider 31, and the movable end of the elastic member 21 slides vertically downward relative to the movable slider 31. There is a sliding friction force between the movable end of the elastic member 21 and the movable slider 31, and the movable slider 31, the fixed slider 32 and the scanning unit 5 remain relatively stationary in the vertical direction. There is a static friction force between the movable slider 31 and the fixed slider 32; when the movable end of the piezoelectric body 22 is shortened by the first set length L1 in the vertical direction, the movable end of the piezoelectric body 22 stops retracting, the needle insertion holding stage of the current needle insertion cycle ends, and the needle insertion approach stage of the next needle insertion cycle begins.

[0131] In S3, the needle withdrawal specifically includes the following contents: the movable end of the piezoelectric body 22 reduces the positive pressure applied to the movable slider 31 through the movable end of the elastic member 21, and at the same time the movable end of the piezoelectric body 22 swings and retracts toward the fixed end of the piezoelectric body 22, driving the movable end of the elastic member 21 to slide and retract toward the fixed end of the piezoelectric body 22 on the outer wall of the movable slider 31, and the movable slider 31 slides vertically downward relative to the fixed slider 32 in the vertical direction to withdraw the needle of the scanning unit 5.

[0132] The scanning imaging method of a scanning tunneling microscope with stable imaging of the present invention can significantly reduce interference within the scanning tunneling microscope body, improve the quality and stability of imaging, and avoid pin collision as much as possible.

[0133] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

[0134] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A scanning tunneling microscope with stable imaging, comprising a microscope body, a signal acquisition and drive module, and a computer, wherein the microscope body and the signal acquisition and drive module are electrically connected, and characterized in that: The scope comprises an outer frame (1), a driving unit (2), a sliding unit (3), a sample holder (4) and a scanning unit (5); the outer frame (1) is hollow inside; the driving unit (2) and the sample holder (4) are respectively arranged at two ends inside the outer frame (1); the sliding unit (3) is arranged on the inner side wall of the outer frame (1); the scanning unit (5) is fixedly arranged at one end of the sliding unit (3) close to the sample holder (4); the driving unit (2) drives the sliding unit (3) to push the scanning unit (5) to advance or withdraw the needle along the length direction of the outer frame (1); The driving unit (2) comprises an elastic member (21) and a piezoelectric body (22), each of the elastic member (21) and the piezoelectric body (22) comprising a fixed end and a movable end, the fixed end of the piezoelectric body (22) being fixedly arranged on the inner wall of the outer frame (1), the fixed end of the elastic member (21) being fixedly connected to the movable end of the piezoelectric body (22), and the movable end of the elastic member (21) driving the sliding unit (3) to slide along the length direction of the outer frame (1).

2. The scanning tunneling microscope with stable imaging according to claim 1, characterized in that: The sliding unit (3) comprises a movable slider (31) and a fixed slider (32); the fixed slider (32) is fixedly arranged on the side wall inside the outer frame (1); the movable slider (31) and the fixed slider (32) are slidably engaged along the length direction of the outer frame (1); the movable end of the elastic member (21) drives the movable slider (31) to slide along the length direction of the outer frame (1); the end of the movable slider (31) close to the sample holder (4) is recorded as the first end, and the end of the movable slider (31) away from the sample holder (4) is recorded as the second end; the scanning unit (5) is fixedly arranged at the first end of the movable slider (31).

3. The scanning tunneling microscope with stable imaging according to claim 2, characterized in that: The scanning unit (5) comprises a piezoelectric scanning tube (52) and a probe frame (51); one end of the piezoelectric scanning tube (52) is fixed to the first end of the movable slider (31); the other end of the piezoelectric scanning tube (52) is fixedly connected to the probe frame (51); and a probe is placed on the probe frame (51).

4. The scanning tunneling microscope with stable imaging according to claim 3, characterized in that: The piezoelectric body (22) further includes a first limit block (221), and the movable slider (31) further includes a second limit block (311), wherein the second limit block (311) is fixedly arranged on the second end of the movable slider (31), and the first limit block (221) is fixedly arranged at the fixed end of the piezoelectric body (22) and at a position opposite to the second limit block (311).

5. The scanning tunneling microscope with stable imaging according to claim 3, characterized in that: The distance d between the second end of the movable slider (31) and the movable end of the piezoelectric body (22) is greater than 0.

6. The scanning tunneling microscope with stable imaging according to claim 3, characterized in that: The outer frame (1) is provided with an opening at one end of the piezoelectric body (22), and a window is provided on a side wall of the outer frame (1).

7. The scanning tunneling microscope with stable imaging according to claim 3, characterized in that: The outer frame (1) is provided with one end of the piezoelectric body (22) at the bottom, and the outer frame (1) is provided with one end of the sample holder (4) at the top; the piezoelectric body (22) is below the movable slider (31).

8. A stable imaging scanning imaging method, using a stable imaging scanning tunneling microscope according to any one of claims 3 to 7, characterized in that: The following steps are involved: S1, the piezoelectric body (22) receives the needle-advancing signal sent by the signal acquisition and driving module, and after the movable end of the elastic member (21) is in squeeze contact with the movable slider (31), the piezoelectric body (22) drives the scanning unit (5) to advance the needle through the elastic member (21) and the sliding unit (3). The needle-advancing process includes n consecutive needle-advancing cycles until the signal acquisition and driving module acquires the tunnel current, at which time the scanning unit (5) stops advancing the needle and starts scanning imaging; Where 0 < n, a needle insertion cycle includes the needle insertion approach phase and the needle insertion holding phase in chronological order; S2, the piezoelectric scanning tube (52) drives the probe holder (51) to move in the XY plane, and the probe scans and images the sample surface; S3, scanning imaging is completed, the piezoelectric body (22) receives the needle withdrawal signal sent by the signal acquisition and driving module, and drives the scanning unit (5) to withdraw the needle through the sliding unit (3).

9. The scanning imaging method for stable imaging according to claim 8, characterized in that: In S1, the needle approach phase also includes the following: The movable end of the piezoelectric body (22) extends along the length direction of the outer frame (1), the elastic member (21), the movable slider (31) and the scanning unit (5) remain relatively stationary, and the elastic member (21), the movable slider (31) and the scanning unit (5) slide vertically upward at a uniform speed relative to the fixed slider (32) as the movable end of the piezoelectric body (22) extends. When the movable end of the piezoelectric body (22) extends in the vertical direction by a first set length L1, the movable end of the piezoelectric body (22) stops extending, the needle approach phase of the current needle insertion cycle ends, and the needle insertion holding phase of the current needle insertion cycle begins. In S1, the needle holding phase also includes the following: The active end of the piezoelectric body (22) reduces the positive pressure applied to the movable slider (31) by the active end of the elastic member (21), and at the same time the active end of the piezoelectric body (22) swings and retracts toward the fixed end of the piezoelectric body (22), driving the active end of the elastic member (21) to slide and retract toward the fixed end of the piezoelectric body (22) on the outer wall of the movable slider (31), and the active end of the elastic member (21) slides vertically downward relative to the movable slider (31). There is sliding friction between the active end of the elastic member (21) and the movable slider (31), and the movable slider (31), the fixed slider (32) and the scanning unit (5) remain relatively stationary in the vertical direction. There is static friction between the movable slider (31) and the fixed slider (32); When the active end of the piezoelectric body (22) is shortened by a first set length L1 in the vertical direction, the active end of the piezoelectric body (22) stops retracting, the needle insertion holding phase of the current needle insertion cycle ends, and the needle insertion approach phase of the next needle insertion cycle begins; In S3, needle withdrawal specifically includes the following: The active end of the piezoelectric body (22) reduces the positive pressure applied to the movable slider (31) by the active end of the elastic member (21), and at the same time the active end of the piezoelectric body (22) swings and retracts toward the fixed end of the piezoelectric body (22), driving the active end of the elastic member (21) to slide and retract toward the fixed end of the piezoelectric body (22) on the outer wall of the movable slider (31), and the movable slider (31) slides vertically downward relative to the fixed slider (32) in the vertical direction, so that the scanning unit (5) retracts the needle.

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